Re: Bought a 2009 VW Sportwagen and the dealer is telling me not to use biofuels....

I have heard that VW does not like folks to use biofuels and may void the warranty.  I just talked to a head mechanic type who went into some details about the 2009, has anyone had problems?  Any suggestions?  The 2009 is apparently somewhat different than some of the older vehicles.  I would really prefer to use biofuels if possible.

Thanks, Jan

Sad but true, the oil companies got their way and the new "clean diesels" were designed NOT to run on more than 5% biodiesel. 2006 was the last model year for VWs which could run B100.

44MPG

Sad but true, the oil companies got their way and the new "clean diesels"

There two problems with the '09s when it comes to biodiesel.  I'm going to give the Reader's Digest version, but I'm missing some of the science, so I hope experts will correct anything I mung up.

The DPF (diesel particulate filter) is designed in such a way that every so often, the engine will inject extra fuel late in the combustion cycle that doesn't combust in the cylinders, but instead is carried to the DPF, which then uses that fuel to burn off the accumulated particles.  This it the crux of both problems.

1) The DPF is both physically designed and computer-mandated to carry out the burn-off at a certain temperature.  It could have been made more flexible, in order to handle different fuels, but it wasn't.  This is a deliberate design choice and is, in my opinion, sabotage against anyone wanting to run biodiesel.  Because tampering with emissions controls is a federal offense, it's as serious as removing the catalytic convertor, in terms of possible penalties.  So no big-name tuner is likely to take the risk of attempting to disable the DPF or retuning it to be more compatible with biodiesel.

2) There is the long-preached problem of oil dilution, which has been used to scare us for years.  Well, the with DPF's late injection, it's actually a real problem.  Since the extra fuel is being injected into the cylinders so late in the ballgame, it doesn't burn and a good portion ends up sticking to the cylinder walls and sliding down into the crankcase, diluting the oil.  For D2, this isn't a problem because the fuel simply burns off in the crankcase due to its low flash point and volatility.  With biodiesel's much-higher flash point (higher than the oil temperature ever gets), it simply stays in the crankcase and oxidizes, thereby promoting corrosion of the engine's internals, as well as reducing the viscosity of the oil, impeding its ability to lubricate.

So, in the '09s, because of it's unique DPF system, B100 is a no-no.  Anything over B20, in fact, might be very harmful because of problem #2.  I don't believe in even trying to disable the DPF because of my beliefs about how we shoudl be treating our atmosphere, but you have to make up your own minds about that one, also keeping in mind that it's against federal law.  So, my solution was to locate the newest non-PD TDI I could (I'm not fond of the PDs either) and make it last a long time.  I'll be picking it up (a white 2-door 2003 Golf, which is what I originally wanted) this weekend.

VW does fully support 5% biodiesel in the '09s, as it has in all TDIs for a few years now, so feel free to use 5%, but I wouldn't go much above 10% if you want your car to last and your warranty to remain intact.

Hope this helps!

-Mike

Very interesting comments Mike. On one hand I like the idea that VW TDIs don't need the AdBlue ... on the other hand, I'd like to be able to move away from fossil fuel.